1. Field of the Invention
The invention relates to an apparatus for retaining the casing engaging slips of a packer or hanger for a subterranean well in an inoperative position during run-in of the packer or hanger into the well.
2. History of the Prior Art
Packers or hangers are probably the most common element utilized in a subterranean well after the installation of the casing. It is common to employ segment-shaped slip elements having peripherally extending teeth formed on their outer surfaces which are cammed into biting engagement with the inner bore wall of the well conduit within which the packer or hanger is to be anchored. Obviously, in order to insert the packer or hanger in the well conduit at a desired location, it is essential that the slips be maintained in a retracted position so as to move freely through the well conduit during the run-in procedure.
Many forms of slip retention mechanisms have heretofore been employed in prior art devices. Such devices have taken the form of shear screws which hold the slips in a retracted position against a spring bias. Alternately, axially shiftable sleeves have been employed to engage or surround the slips and thus hold them in an inoperative position.
All of the prior art devices have been characterized by not being failsafe. It has always been possible during the run-in of a packer or hanger to encounter an obstruction in the well which will effect a release of the slip retention mechanism and result in the inadvertent setting of the slips prior to the packer or hanger reaching its desired position in the well. The time and expense of releasing and retrieving an inadvertently set packer or hanger is well known to those skilled in the art.